1. Field of the Invention
The present invention relates to a magnetic tape apparatus, and more particularly to a magnetic tape apparatus having means for preventing dirt from being accumulated on a magnetic tape.
2. Description of the Related Art
Magnetic tape apparatus transport a magnetic tape to write information on the magnetic tape and read information from the magnetic tape. The magnetic tape produces dirt of magnetic particles when it contacts a magnetic tape transport path and magnetic heads. When the produced dirt is attached to the magnetic tape, it causes a failure to write information on the magnetic tape and read information from the magnetic tape. To prevent such a failure, the magnetic tape apparatus usually have a tape cleaner for scraping the attached dirt off the magnetic tape.
The tape cleaner is usually positioned near a magnetic head. The distance between the tape cleaner and the magnetic tape is often greater than the length of a data block recorded on the magnetic tape. If the magnetic tape is continuously reciprocally moved a distance smaller than the distance between the tape cleaner and the magnetic tape in order to record information and reproduce information from one data block, then an area is developed on the magnetic tape which is held in contact with the magnetic head but kept out of contact with the tape cleaner. As a result, dirt particles are gradually collected in the area, tending to cause a failure to write information on the magnetic tape and read information from the magnetic tape.
It is therefore an object of the present invention to provide a magnetic tape apparatus which prevents dirt from being accumulated on a magnetic tape even when the magnetic tape is continuously reciprocally moved in a small interval for recording information on and reproducing information from the magnetic tape.
According to the present invention, there is provided a magnetic tape apparatus connected to a computer system, for recording data on and reproducing data from a magnetic tape as instructed by the computer system. The magnetic tape apparatus comprising a magnetic head for recording data on and reproducing data from the magnetic tape, a tape cleaner disposed near the magnetic head for contacting the magnetic tape to clean the magnetic tape, and operation monitoring means;for monitoring movement of the magnetic tape. The operation monitoring means have a function for monitoring reciprocating movement of the magnetic tape in a short interval, and, if the magnetic tape is reciprocally moved at least a predetermined number of times in a predetermined range, for performing a forced cleaning process to cause a drive device for the magnetic tape. The drive device transport the magnetic tape in a transported range greater than the predetermined range to bring an area on the magnetic tape which has been contacted by the magnetic head into contact with the tape cleaner in the forced cleaning process.
The operation monitoring means may comprise means for calculating information of a position of the magnetic tape from information of an operation status and a rotational speed of a reel for transporting the magnetic tape, which information is supplied from a drive circuit for controlling the rotation of the reel, measuring the position of the magnetic tape from a previously stopped position as a reference point, updating the reference point into a presently stopped position if the magnetic tape has moved from the reference point beyond the predetermined range and stopped, refraining to update the reference point and accumulating the number of times that the magnetic tape has been stopped if the magnetic tape has moved from the reference point and stopped within the predetermined range, and instructing a control means for controlling the drive circuit to perform the forced cleaning process if the accumulated number of times exceeds a predetermined number of times.
Alternatively, the operation monitoring means may comprise means for calculating information of a position of the magnetic tape from information of an operation status and a rotational speed of a reel for transporting the magnetic tape, which information is supplied from a drive circuit for controlling the rotation of the reel, measuring the position of the magnetic tape from a previously stopped position as a reference point, updating the reference point into a presently stopped position if the magnetic tape has moved from the reference point beyond the predetermined range and stopped, refraining to update the reference point and accumulating the number of times that the magnetic tape is transported back if the magnetic tape is transported back in the predetermined range, and instructing a control means for controlling the drive circuit to perform the forced cleaning process if the accumulated number of times exceeds a predetermined number of times.
The forced cleaning process may comprise a process of transporting the magnetic tape from a start point for a first distance in a predetermined direction, stopping the magnetic tape, transporting back the magnetic tape from a stopped point for a second distance in excess of the first distance, stopping the magnetic tape, transporting the magnetic tape again in the predetermined direction, and stopping the magnetic tape at the start point.
Alternatively, the forced cleaning process may comprise a process of, while the magnetic tape is being transported in a direction from a process of recording data in and reproducing data from a presently processed data block to a process of recording data in and reproducing data from a next data block, transporting the magnetic tape from an end point of the presently processed data block for a first distance in the same direction as the direction, stopping the magnetic tape, transporting back the magnetic tape from a stopped point for a second distance in excess of the first distance, stopping the magnetic tape, transporting the magnetic tape again in the direction, and stopping the magnetic tape at a start point of the next data block.
The tape cleaner may comprise a single tape cleaner disposed in a position opposite to a reel by which a beginning of the magnetic tape is wound, as viewed from the magnetic head. The predetermined range monitored by the operation monitoring means may extend 2 through 4 times the distance between the magnetic head and the tape cleaner, and the transported range of the magnetic tape in the forced cleaning process may extend 3 through 6 times the distance between the magnetic head and the tape cleaner.
Alternatively, the tape cleaner may comprise two tape cleaners disposed one on each side of the magnetic head. The predetermined range monitored by the operation monitoring means may be substantially the same as the distance between the two tape cleaners, and the transported range of the magnetic tape in the forced cleaning process may extend 1 through 3 times the distance between the two tape cleaners.
With the above arrangement, the magnetic tape apparatus monitors the movement of the magnetic tape in the short interval. If the magnetic tape is repeatedly moved at least a predetermined number of times in the short distance, then the magnetic tape is moved a large distance to bring an area on the magnetic tape which has been repeatedly moved on the magnetic head into the tape cleaner. Therefore, dirt is prevented from being accumulated on the magnetic tape even when the magnetic tape is repeatedly transported back and forth.
The above and other objects, features, and advantages of the present invention will become apparent from the following descriptions based on the accompanying drawings which illustrate examples of preferred embodiments of the present invention.